linux-kernel - Re: [PATCH v5 07/10] crypto: ccp: Add preferred access checking method

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Message-ID: <CAAH4kHaAqh1R6CGBKXNsO+uQnscwGo0Y06MTny8CebSWK9QMaw@mail.gmail.com>
Date: Tue, 12 Nov 2024 11:47:51 -0800
From: Dionna Amalie Glaze <dionnaglaze@...gle.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, 
	Ashish Kalra <ashish.kalra@....com>, John Allen <john.allen@....com>, 
	Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>, 
	linux-coco@...ts.linux.dev, Sean Christopherson <seanjc@...gle.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Michael Roth <michael.roth@....com>, Luis Chamberlain <mcgrof@...nel.org>, 
	Russ Weight <russ.weight@...ux.dev>, Danilo Krummrich <dakr@...hat.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Tianfei zhang <tianfei.zhang@...el.com>, Alexey Kardashevskiy <aik@....com>, linux-crypto@...r.kernel.org
Subject: Re: [PATCH v5 07/10] crypto: ccp: Add preferred access checking method

On Mon, Nov 11, 2024 at 2:46 PM Tom Lendacky <thomas.lendacky@....com> wrote:
>
> On 11/7/24 17:24, Dionna Glaze wrote:
> > sev_issue_cmd_external_user is the only function that checks permissions
> > before performing its task. With the new GCTX API, it's important to
> > establish permission once and have that determination dominate later API
> > uses. This is implicitly how ccp has been used by dominating uses of
> > sev_do_cmd by a successful sev_issue_cmd_external_user call.
> >
> > Consider sev_issue_cmd_external_user deprecated by
> > checking if a held file descriptor passes file_is_sev, similar to the
> > file_is_kvm function.
> >
> > This also fixes the header comment that the bad file error code is
> > -%EINVAL when in fact it is -%EBADF.
>
> Same comment as before. This commit merely creates a helper function, so
> this commit message is not appropriate.
>

Is this a meta-comment about how the commit presupposes being in a
series with a goal, but should have a self-contained commit message? I
don't know what "same comment as before" you're referring to.
How about this:

crypto: ccp: Add file_is_sev to identify access

Access to the ccp driver only needs to be determined once, so
sev_issue_cmd_external_user called in a loop (e.g. for
SNP_LAUNCH_UPDATE) does more than it needs to.

The file_is_sev function allows the caller to determine access before using
sev_do_cmd or other API methods multiple times without extra access
checking.

This also fixes the header comment that the bad file error code is
-%EINVAL when in fact it is -%EBADF.




-- 
-Dionna Glaze, PhD, CISSP, CCSP (she/her)